Research on oil adsorption capacity of carbonized material derived from agricultural by product corn cob corn stalk rice husk using in oily wastewater treatment

105 Research on Oil Adsorption Capacity of Carbonized Material Derived from Agricultural by-product Corn Cob, Corn Stalk, Rice Husk Using in Oily Wastewater Treatment Nguyen Thanh Ha*,

105

Research on Oil Adsorption Capacity of Carbonized Material Derived from Agricultural by-product (Corn Cob, Corn Stalk,

Rice Husk) Using in Oily Wastewater Treatment

Nguyen Thanh Ha*, Le Van Cat, Pham Vy Anh, Tran Thi Thuy Lien3*

Department of Environmental chemistry, Institute of Chemistry,

Vietnam Academy of Science and Technology

Received 17 May 2016 Revised 15 August 2016; Accepted 01 September 2016

Abstract: Oily wastewater discharged from machinery producing, mining, storage service, marine

transporting is one of the polluting sources to receiving waterbody Adsorption onto carbonized material derived from agricultural by-products are proved to be the promising treatment for this type of wastewater Experiments implemented with the agro-wastes including: corn cob, corn stalk and rice husk with carbonizing temperature of 300-600 oC and retention time of 1-3h According to the results of all carbonized materials, the decrease of oil adsorption accosiated with higher pyrolysis temperature, as well as longer retention duration Under the same carbonizing conditions, the carbon derived from corn stalk have the higher adsorption capacity The highest oil sorption capacity of 6.4 g/g is of corn stalk derived carbon with temperature of 300 oC, retention time of 1h; while the lowest one of 2.33 g/g is of material derived corn cob with temperature of 600 oC, 1h The oil adsorption capacity is closely related to the porosity and oleophilic groups on the surface

of the material The results indicated that materials made from agricultural by-products, corn stalk

in particular, are promising for oily wastewater treatment

Keywords: Corn cob, corn stalk, rice husk, oily wastewater

1 Introduction *

In Vietnam, the redundant of agricultural

by-products is one of the most serious problem

In present, the most common treating of these

agro-wastes is to dispose as solid waste or, in

lesser extent, to produce fuel, plant pot The

disposal of wastes causes the surrounding

environmental pollution, discharging

greenhouse gas as result of their biodegrading

The carbon derived biomass has advantage of

low cost, abundant, environmental friendly,

_

*

Corresponding author Tel.: 84-937308188

Email: nth.et.vn@gmail.com

high C content, specific porosity of cellulose derived material, accordant with C based material production by carbonizing The product is able to use for treatment wastewater, especially oil contaminated, occurring in industrial processing, maritime transporting [10] There are many researchers targeting to remove oil by using agricultural by-products Kumagai et al (2007) investigated the oil adsorption by using carbonized rice husk The result indicated that the biochar produced at 600

o

C is able to use for oil adsorption [4] Nwadiogbu et al (2014) acetylated the corn cob

to increase the hydrophobicity [6] Suni et al (2004) used the by-product of peat excavation,

cotton grass fiber to adsorb the oil [7]

Adsorption onto carbonized agricultural

by-products are proved to be the most effective

treating methods for organic compounds in

wastewater, with the oil removal efficiency of

about 99 % [8], inexpensiveness and ease of

operation [1]

Among of agricultural wastes in Vietnam,

rice husk, corn cob and corn stalk are the most

common, significant high volume for producing

low cost adsorbents Therefore, this research

aims to produce low cost carbon material from

the aforementioned by-products in order to

remove the oil in industrial wastewater

2 Method

2.1 Precursor collecting and characterization

The agricultural by-products used in this

study include: corn cob; corn stalk; rice husk

All samples are collected from waste disposal

location in Luong Son district, Hoa Binh

province and Hanoi The sample is pretreated

by dried in room temperature The corn cob is

grinded and sieved to achieve the particle of 3-5

mm diameter The stalk is cut into pieces with

average length of 20-30 mm After that, all

samples are stored in dried bottle

2.2 Material carbonizing

The weighted samples are placed into

horizontal reactor Then, the carbonization

implemented by using the furnace Emin

SX2-5-12 (China) is occurred in different temperature

and retention time After the carbonization, the

char sample is cooled by air, dried in 105 oC to

remove the humidity The carbon sample is

weighted to determine the carbonization

efficiency The samples are denoted as X-Y-Z,

whereas X: name of raw material; Y:

carbonization temperature; Z: retention time

2.3 Analytical method

Porous volume of carbon sample are

determined according to distilled water

pycnometer method [2] The maximum oil absorption capacity of char sample is determined according to the method of ASTMF726-99 [5] using weight difference analyzing Oil sample used is commercial DO with specific density in 15 oC of 820-860 kg/m3, dynamic viscosity in 40 oC of 2 - 4,5 cSt (according to Saigonpetro Co Ltd) The SEM image of sample is obtained by using Jeol 5300 (Japan) The IR spectrum is obtained by using Nicolet iS10 from Thermo Scienticfic, USA TG-DTA of sample is collected by TGA209F1, from NETZSCH, Germany

3 Results and discussion

3.1 Effect of carbonizing conditions

Effect of carbonizing temperature:

Figure 1 showed the TGA result of precursor samples, there is dramatically change

in precursor mass within temperature of

300-600 oC, with value of about 50% This could be explained by the thermal degradation of hemicellulose and cellulose [9] In concluded, the carbonizing temperature used in this research is about 300 - 600 oC, which could cause significant change in structure of samples

Figure 2 illustrated the effect of carbonizing temperature to the quality of chars In general, compared at similar carbonizing conditions, the oil adsorption and pore volume of char derived from corn stalk is the largest, then followed by rice husk and corn cobs At temperature of 300

o

C, retention time of 1h, the oil adsorption capacity and pore volume of char derived from corn stalk, rice husk and corn cob are 6.4 g/g, 6.9 mL/g; 5.7 g/g, 6.7 mL/g and 2.3 g/g, 2.6 mL/g, respectively

The result indicated that, for 3 precursors, the increase of carbonizing temparature leads to the decrease of oil adsorption capacity as well

as pore volume of each chars, but with different trends At same retention time (1h), the oil adsorption capacity corn stalk derived char reaches the maximum of 6.4 g/g at 300 oC, decreased constantly to the minimum of 3.9 g/g

reached at 600 oC The trend of pore volume

change of corn stalk chars is fluctuated It

reaches the highest of 6.9 g/L at 300 oC, then

dramatically decreased to the lowest of 4.1 g/L

at 500 oC, followed by the increase to 4.6 g/L at

600 oC There are similar variability trends

between oil adsorption and pore volume of corn

cob as well as rice husk carbon samples The

highest value of oil adsorption capacity and

pore volume of rice husk derived chars are 5.7

g/g and 6.7 g/L at 300 oC, followed by the constant decrease and reached the lowest of 3.4 g/g and 3.6 g/L at 600 oC, respectively There is slightly decrease of oil adsorption capacity and pore volume of corn cob chars with the upturn

of carbonizing temperature The highest of them are 2.3 g/g and 2.6 g/L at 300 oC, while the lowest of 1.7 g/g and 2.2 g/L are reached at

600 oC

g

Figure 1 The TGA result of precursor samples

Figure 2 Effect of carbonizing temperature

Figure 3 Effect of retention time

Effect of retention time

Figure 3 showed the effect of carbonizing

retention time Similar to temperature, the

retention time of carbonization effects

significantly to the character of biochars derived

from corn stalk and rice husk; negligible with

ones from corn cob In general, the longer

retention time is, the lower value of oil adsorption

capacity and pore volume of chars For all chars,

the highest value of them are reached at 1h of

retention time, while the lowest achieved at 3h of

retention time The oil adsorption capacity of corn

stalk chars at 1h and 3h of retention time are 6.4

and 2.4 g/g, while the value the pore volume are

6.9 and 3.1 mL/g, respectively

According to the result, the effect of

carbonizing conditions (temperature, retention

time) to oil adsorbing characters of chars (oil

adsorption capacity; pore volume) is

significant To better understand the structure of

pore system and functional groups on surface,

which contribute to oil adsorbing characters, the

SEM and FT-IR experiments are implemented

3.2 Discussion

As indicated from the aforementioned

result, the samples produced at carbonizing

condition of 300 oC and 1h have the best

character for oil adsorption Therefore, these

samples of all precursors are chosen for further

research in order to investigate the appearance

structure of pore, functional group

Figure 4 The SEM image of chars produced at 300

o

C, 1h (Corn cob (a, d), Corn stalk (b, e),

rice husk (c, f))

The result of SEM indicated that, with all of the char samples, the diameter of pore are about

1 - 4 µm The pore diameter of corn cob, corn stalk and rice husk derived char are about 1 - 2,

2 - 4 and 2 µm, respectively The oil droplet in water has the diameter of about 0.5 - 5 µm Therefore, the pore of char samples are favorable for oil adsorption The diameter of pore of char

samples is classified as macro-pore originated

from the precursor Gray et al (2014) suggested

the shrinkage of pore structure increase with the

upturn of temperature [3], resulting the destructive

of macro-pore This could explain the reason of

decrease of oil adsorbing character of char sample

with elevation of carbonizing temperature

The large pore of corn stalk could be one of

the reasons explaining for the highest value of

pore volume, as well as oil adsorption capacity

However, the diameter of pore of rice husk char

is relatively small although the oil adsorbing

character of this char is comparable with one of

corn stalk char It can be explained by the

structure of pore As illustrated in SEM results,

the pore structure is complicated, crisscrossed

by the system of hollow shaped pore This

could increase the pore volume of char, create

more adsorption site of oil

Figure 5 The IR spectrum of precursor and char

samples (A: Corn cob; B: corn stalk; C: rice husk)

The result of FTIR spectra are performed in

Figure 5 and 6 In general, the spectra graph of

all precursors are relatively similar, which

peaks include: 3330-3350 cm-1 (-OH stretching

of hydroxyl group, phenol, acid carboxylic),

2850-2950 cm-1 (-C-H stretching of aliphatic),

1450-1650 cm-1 (-C=C- stretching of aromatic),

1650 - 1750 cm-1 (-C=O group of ester

(ascribed to hemicellulose, acid carboxylic,

aldehyde), 1036 - 1075 cm-1 (-C-O stretching in

cellulose, hemicellulose and primary alcohol),

750 - 800 cm-1 (-C=C- bending of aromatic),

550 - 650 cm-1 (C is out of plane -C-H band,

alkanes, -Si-O-Si- especially for rice husk

sample), 480 - 590 cm-1 (-OH out of plane bending) [3, 6]

Compared to the result of precursors, one of char samples produced at 300 oC, 1h indicate the significant difference, especially for corn cob and corn stalk derived chars Beside the peaks of –OH stretching of hydroxyl group,

-CH stretching of aliphatic similar with ones of precursor sample, the peaks of –CH deformation in –O-C=O-CH3 appear intensity at about 1359 – 1440 cm-1 [6] This could be the result of hemicellulose and cellulose degradation in temperature of about 200 – 350

o

C [8]

The result indicate that, the increase of carbonizing temperature leads to the diminishing of functional group abundance and diversity [3] Except for rice husk derived samples, there is a significant increase of –CH aliphatic peak, which is of interest as positively correlating with hydrophobicity in biochars However, the peaks representing for hydrophilicity of biochars such as –C=C- of aromatic, -C=O and –OH of ionisable hydroxyl group, show negligible change

From all of the result reported, it could be concluded that:

i The higher carbonizing temperature is, the longer retention time is, then the lower value of oil adsorbing character of chars (oil adsorption capacity, pore volume)

ii The pore structure and chars are favorable the adsorption of oil

iii Except for rice husk chars, the carbonization results into the increase of hydrophobicity of biochar, while there is slightly change in hydrophilicity

For further investigation, the oleophilic fluid produced in carbonization should be investigated According to Kumagai et al (2007) [4], there is evident that this fluid contributes to the oil adsorption Furthermore, the water uptake capacity of biochar causes negative effect to apply the biochar for oil adsorbing The result of maximum water uptake capacity of chars derived from corn stalk, corn cob and rice husk (which is not showed in this

article) are relatively high The future

investigation would include the research of

lower water uptake capacity

4 Conclusion

The experiments indicated the oil

adsorption capacity of biochars derived from

agricultural by-products such as corn stalk, corn

cob and rice husk The highest oil adsorption

capacity of char samples are obtained at

temperature of 300 oC, retention time of 1h The

increase of carbonizing conditions result in the

downturn of oil adsorption of chars The oil

adsorption character of corn cob and rice husk

chars are much better than one corn cob,

showing the promise material for oil adsorbent

Further research is needed to investigate the

oleophilic fluid as well as the method to

decrease the water uptake capacity

Acknowledgement

The authors thank to the Institute of

Chemistry, Vietnam Academy of Science and

Technology for funding, facilitating the

condition and equipment to implement the

research VHH.2016.2.17

References

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[2] Cat L.V (2002), Adsorption and ion exchange

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[3] Gray M, Johnson M.G, Dragila M.I, Kleber M, (2014) “Water uptake in biochars: the roles of porosity and hydrophobicity”, Biomass and Bioenergy 61, 196 - 205

[4] Kumagai S, Noguchi Y, Kurimoto Y, Takeda

K, (2007), “Oil adsorbent produced by the carbonization of rice husks”, Waste Manage

27, 554 - 561

[5] Li H, Liu L, Yang F (2012), “Hydrophobic modification of polyurethane foam for oil spill cleanup”, Marine Pollut Bulletin 64,

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[6] Nwadiogbu J.O, Okoye P.A.C, Ajiwe V.I, Nnaji N.J.N, 2014, “Hydrophobic treatment of corn cob by acetylation: Kinetics and thermodynamic studies”, J Environ Chemical Engineer 2 (3), 1699 - 1704

[7] Suni S, Kosunen A.L, Hautala M, Pasila A, Romantschuk M (2004), “Use of a by-product

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[8] Pazó J.A, Granada E, Saavedra A, Eguia P, Collazo J (2010), “Uncertainty determination methodology, sampling maps generation and trend studies with biomass thermogravimetric analysis” Int J Mo Sci 11, 3660-3674 [9] Parparita E, Berbu M, Uddin M.A, Yanik J, Vasile C (2014), “Pyrolysis behaviors of various biomasses”, Polymer Degrad Stab 100, 1-9

[10] Viraraghavan T, Mathavan G.N (1988),

“Treatment of oil-in-water emulsions using peat”, Oil & Chemical Pollut 4, 261 - 280

Nghiên cứu khả năng hấp phụ của vật liệu than hóa có nguồn gốc từ phế liệu nông nghiệp (lõi ngô, thân ngô, vỏ trấu) nhằm

sử dụng trong xử lý nước thải nhiễm dầu

Nguyễn Thanh Hà, Lê Văn Cát, Phạm Vy Anh, Trần Thị Thúy Liên 3*

Phòng Hóa Môi trường, Viện Hóa học, Viện Hàn lâm Khoa học và Công nghệ Việt Nam

Tóm tắt: Nước thải nhiễm dầu mà được xả thải từ quá trình chế tạo cơ khí, khai thác mỏ, lưu giữ

kho bãi, vận chuyển đường biển là một trong những nguồn ô nhiễm đưa vào thủy vực Quá trình hấp phụ lên vật liệu than hóa có nguồn gốc từ phế liệu nông nghiệp được coi là phương pháp xử lý có triển vọng đối với loại nước thải này Các thí nghiệm được tiến hành với các phế phẩm nông nghiệp bao gồm: lõi ngô, thân ngô và vỏ trấu với nhiệt độ than hóa từ 300-600 oC, thời gian lưu từ 1-3 h Dựa trên các kết quả thu được từ tất cả sản phẩm than hóa, nhiệt độ than hóa càng cao, thời gian lưu càng lâu thì khả năng hút dầu càng thấp Ở cùng điều kiện than hóa, mẫu than có nguồn gốc từ thân ngô có khả năng hút dầu cao hơn các mẫu than có nguồn gốc từ lõi ngô và vỏ trấu Mẫu than thân ngô được chế tạo ở 300 oC, thời gian lưu 1h có dung lượng hấp phụ dầu cao nhất ở mức 6,4 g/g; trong khi dung lượng hấp phụ dầu thấp nhất đạt 2,3 g/g thuộc về mẫu than từ lõi ngô mà chế tạo ở 600 oC, 1h Dung lượng hấp phụ dầu có mối tương quan chặt chẽ với độ xốp và nhóm chức ưa dầu trên bề mặt than Các kết quả chỉ ra rằng sự hấp phụ dầu lên vật liệu được chế tạo từ phế liệu nông nghiệp, đặc biệt là thân ngô, là phương pháp khả quan trong xử lý nước thải nhiễm dầu